Constructing surface oxygen defects at CuO-Co3O4 interface to boost toluene oxidation over CuO/Co3O4 catalysts

As a typical heterogeneous catalytic process, the catalytic combustion of toluene over Co3O4-based catalysts is strongly depends on the surface properties of catalysts, especially the concentration of surface oxygen defects. Here, a novel way was proposed to construct chemically bonded CuO-Co3O4 interface by chemical deposition of CuO onto Co3O4 nanoflowers. The interfacial refinement effect between CuO and Co3O4 support disrupted the ordered atomic arrangement and created countless unsaturated coordination sites at CuO-Co3O4 interface, inducing a significant generation of surface oxygen defects. Surface-rich oxygen vacancies enhanced the capacity of 20%CuO/Co3O4-R to adsorb and activate oxygen species. Benefiting from this, 90 % toluene conversion was reached at 228 °C over 20%CuO/Co3O4-R, which was much lower than that over 20%CuO/Co3O4-S prepared by impregnation method and CuO/Co3O4-mix obtained by mechanically mixing way. In-situ DRIFTS analysis revealed that toluene could be directly decomposed into benzaldehyde at the highly defective CuO-Co3O4 interface, leading to toluene oxidation following the path of toluene → benzaldehyde → benzoate → maleic anhydride → water and carbon dioxide over 20%CuO/Co3O4-R, which was significantly different from decomposition mechanism over 20%CuO/Co3O4-S. Additionally, 20%CuO/Co3O4-R displayed terrific recyclability and outstanding stability, showing good application potential.